Original Research| Volume 25, ISSUE 1, P35-39, January 2006

Download started.


Oxygen conservation during long-distance transport of ventilated patients: assessing the Modified Circle System

      Introduction: The Modified Circle System was developed to reduce the amount of oxygen required for long-distance transportation of ventilated patients. Formal testing of the system has never been documented. Various aspects of the system were tested, with the study broken into four parts.
      Methods: Bench testing was performed with a test lung that simulated two different lung compliances. Four ventilators were tested with the system. The four parts to the study were oxygen flow rates, position of oxygen inflow, pressure drop across the system, and specific testing with the LP 10 ventilator.
      Results: The minimum oxygen flows required to maintain forced inspiratory oxygen (FiO2) higher than 0.93 over a range of ventilator and lung settings was 1.5 L/min. The oxygen inflow is best connected directly to the CO2 absorber unit. A significant pressure drop occurs across the system, which increases progressively with higher ventilator pressures. The LP 10 does not allow improved oxygen conservation when recycling gases via its air inlet port.
      Conclusion: The study provides previously unknown, clinically important information regarding the performance of the Modified Circle System.
      To read this article in full you will need to make a payment

      Purchase one-time access:

      Academic & Personal: 24 hour online accessCorporate R&D Professionals: 24 hour online access
      One-time access price info
      • For academic or personal research use, select 'Academic and Personal'
      • For corporate R&D use, select 'Corporate R&D Professionals'


      Subscribe to Air Medical Journal
      Already a print subscriber? Claim online access
      Already an online subscriber? Sign in
      Institutional Access: Sign in to ScienceDirect


        • Lowes T
        • Sharley P
        Oxygen conservation during long distance transport of ventilated patients.
        Air Med J. 2005; 24: 164-171